Continuous carrier relaying



@damw June 18, 1935.. I

R. M. SMITH CONTINUOUS CARRIER RELAYING Filed Dec. 22, 1933 2 Sheets-Sheet 1 Fllg,

l 8 Va/fage Bias and paws/ flaw in fa line P/afe Bail-cry I I7 ihfo line x] FF WITNESS INVENTOR fiay M Sm/7h I ATTORNEY June 18, 1935.

R M. SMITH 2,005,172 CONTINUOUS CARRIER HELAYING Filed Dec. 22, 1933 2 Sheets-Sheet 2 CHI 3 CHE CR2 To Transmifier P/afe C/rcuif (Opening Circuif Sfop-s Carrier) Carrier Carnra/ 2 59 V0 lfag aresfra in!- 66 67 W winding: of CHI/3 48 CMP 48 4.9 Phi? I Ground Un balance .l fra fec Wan fbr fire pera/le/ line Bac/wup Pro fee fl 0/) Ca rriel' Fai/ure Ind/ca: fion WITNESS nacarrier, car/e; INVENTOR Giff/ r 002257;

ATTORNEY Patented June 18, 1935 UNITED STATES 2,005,172 CONTINUOUS CARREER RELAYING Roy M. Smith, North Arlington, N.

Electric 85 Manufacturing to Westinghouse J., assignor Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application Claims.

This invention relates to means for making the continuous carrier relaying system for transmission-line protection practical, and it has particular relation to means for preventing faulty operation when there is a sudden reversal of fault-current in a sound line-section during the process of segregating a faulty line-section from the system.

The expression continuous carrier relaying is utilized in contradistinction to intermittent carrier relaying, an example of which is shown in Fig. 8 of the Scott Patent 1,765,887, patented June 24, 1930. In the continuous carrier relaying system, the carrier current is left on the line at all times except when there is a fault in the line-section being protected,,at which time the carrier current must be removed from both ends of the line in order to permit instantaneous tripping. In the intermittent carrier relaying system there is normally no carrier-current superposed on the line, but in the event of a fault accompanied by power-flow from the line to the bus at either end, carrier-current is suddenly superposed on purpose of preventing tripping at the other end, the tripping relays being given a suitable time-hesitation or sluggishness of action, of about three cycles, in order to give the carr'er-current relays time to inhibit the tripping action if the fault is not in the line-section being protected. laying systems utilize, or may utilize, carriercurrent transmitters of the same frequency at each end of the line-section being protected.

Heretofore, one of the principal objections against the continuous carrier system, which has helped to lend weight to the intermittent carrier system in spite of the inherent time-hesitation necessarily introduced in every operation of the latter, has been the circumstance that it is possible for a transmission system to be so operated, at times, that when a fault occurs in a linesection other than the sound section being protected, the fault-current at first flows through the sound section in one direction, removing carrier from one end and leaving it on the other end, and then, when the fault-current is partly but not altogether interrupted in the faulty section, the fault-current may suddenly reverse in the sound section being protected, and flow through it in the opposite direction. This sudden reversal of fault-power-flow in the sound line will cause carrier to be removed from the end which was formerly transmitting it, and to be restored to the end at which it had been interrupted, but unless an objectionable time-hesitation is introduced in the operation, this removal of carrier would be faster than the restoration of carrier, in continuous-carrier-current relaying systems as commonly heretofore designed. My present invention provides means for overcoming this December 22,

1.933, Serial No. 703,610

difficulty, while correctly operating without timehesitation under other or normal relaying con ditions.

With the foregoing and other objects in view, the invention consists in the system, combinations, apparatus and methods hereinafter described and claimed and shown in the accompanying drawings, wherein Figure l is a diagrammatic view of circuits and apparatus embodying my invention in an illustrative form;

Fig. 2 is a corresponding schematic or across the-line diagram of the same system; and

Figs. 3 and 4 are sin le-line diagrams referred to in the explanation of the operation.

The invention is illustrated in application to a double-circuit transmission system comprising two three-phase lines I, 2, connected to a common bus 3. The relaying equipment is shown in detail for only one end of the line 2, but as both ends of both lines are substantially identical, one illustration and description will suffice for all. The line i is provided with a circuit breaker 4 having a trip coil 5 which is energized from a suitable trip circuit 6 not shown in detail, the same being substantially equivalent to the trip circuit which is shown and hereinafter described, ion the other line 2.

The line 2 is provided with a circuit breaker 1 having a trip coil 8 and a trip-circuit conductor 9, the control of which embodies the means forming the subject matter of the present invention.

The line 2 has superposed thereon carrier cur rents of relatively high frequency, as a means for securing instantaneous tripping for all faults in the line-section to be protected. This carrier current is produced, at each end of the lineseotion, in a transmitter H which is indicated schematically by a rectangle, as the details of it are not necessary to an understanding of the present invention. It may be a transmitter similar to that which is shown in the application of William A. Lewis and Robert D. Evans, Serial No. 660,342, filed March 11, 1933, for Protective relay systems. The transmitter is provided with a plate circuit GEL-CR2, the opening of which instantly interrupts the transmission. The transmitter is also provided with a transmitter supervisory relay TS having backor break-contacts i. which are broken when the relay is energized and made when the relay is deenergized, as described and claimed in the Lewis and Evans application just mentioned.

The carrier-current equipment at each end of the line 2 also includes a receiver l3 which is indicated only schematically, but it may be substantially as shown and described in the aforementioned Lewis and Evans application. The receiver 13 serves to energize a receiver relay RR having two backor break-contacts l4 and i5 and one frontor make-contact I 6, the break-contacts I 4 and i 5 being opened when the receiver relay RR is energized, and the make-contact to being closed when the receiver relay RR is energized.

The transmitter and receiver 5 l and i3 are cou pled to phase-conductor C of the transmission line 2 by means of tap connections on an inductor or auto-transformer l1, and a combined coupling capacitor and capacitor-p0tentiometer designated in its which constitutes the subject-matter of an application of Paul O. Langguth and William A. Lewis, Serial No. 703,608, filed December 22, 1983, for a Coupling capacitor system.

Interposed between the inductor H and the coupling device I8 is a fuse IS, the terminals of which are connected to ground through gap devices 2| and 22. Gap 2 2, which is connected to the terminal of the inductor i7, is set closer than gap 2| so that, in case a high voltage should reach the coupling lead, the gap 22 would discharge first and divert the surge to ground. In case of power current following the discharge, the rush of current through the fuse 19 to this gap 22 would blow the fuse. Upon the blowing of the fuse t9 the voltage across the other gap 2| would then rise to a value sufficient to discharge this other gap, thus permitting the fuse to clear, and isolating the carrier-current equipment. The are across the gap 2! may continue until it is cleared by the circuit breakers at the ends of the line.

The carrier-current equipment is illustrated as being connected from the phase-C conductor of the line, to ground.

The coupling-capacitor equipment includes a string of capacitors 23 which are connected between the phase-C conductor and a drain coil 24, the other terminal of which is grounded, the carrier-frequency coupling connection being made between the drain coil and the last capacitor unit of the string 23. The same capacitor string is utilized as a capacitor-potentiometer which is tapped off at an intermediate point 25, from which a circuit is lead through a choke coil 25 to a potential transformer 2'! which is protected by a gap device 28. The secondary circuit of the voltage regulation of the device.

understood that a are provided with three phases of the carriercurrent connection is utilized only in phase This ground directional relay is provided with two torques, both tending to operate the relay against the pull of a light restraining spring 35. One torque is a voltage-bias torque produced by voltage alone, and the other torque is a powerdirectional torque produced by the product of ground current and residual voltage multiplied by the sine of some predetermined angle plus the angle existing between the ground current and the residual voltage. The voltage torque is strong enough to actuate the relay when the residual voltage exceeds a predetermined value, but it is not so strong that it will overcome the directional torque whenever a current exceeding the minimum operating point of the over-current element In is flowing in the reverse direction. The ground directional element CHB is provided with one brealocontact 37 and one make-contact 38. It is provided with a current winding 5'9 and a volt= age winding id, which are energized, respectively, from the neutral circuits of a set of line-current transformers ii and a residual potential transformer An instantaneous imbalanced-current relay (J]hP.-This relay consists of three mechanically independent elements t l, 45 and 46 each having a current-responsive actuating coil and a currestraining coil, so that each eleil ent responds to the diiierence between two of the line-currents supplied by the current transformers ii. Each of the three elements of the instantaneous unbalanced-current relay 0MP has one make-contact il and one break-contact 48.

Two instantaneous phase overcurrentrelays Ph. A. and Ph. C'.The Ph. A relay is energized from the phase-A line-current supplied by the current transformer 4 I, and is provided with one break-contact 69 and one make-contact 5D.

phase-C line-current that is supplied by the current transformer 41. This relay element is provided with two make-contacts 5| and 52 re spectively.

An instantaneous CHV3.--This relay is phase directional relay composed of four torqueproducing elements mechanically coupled together, so that the torques add algebraically. Each torque-producing element may be of either the induction-disc type or the galvanoineter type, as previously explained in connection with the ground directionalirelay CHB. For convenience or" illustration, the instantaneous phase directional relay CHV3 is shown as comprising two discs 53 and 54 which are operated on by four'magnetic elements 55, 55, 57 and 58 of a common watt-meter type, each comprising heavy, current-winding 59 and a voltage-winding 50.

iii are opened and closed.

The instantaneous phase directional relay CHVS is normally held against the operation of the spring 63, so that the break-contacts 6| are normally closed, as illustrated, and the make- The current coil 59 voltage coil, to the high-current, low-voltage supply characteristic of a current coil. The current coil 59 is utilized because of its much better space factor than is obtainable with a voltage coil, this being due to the fact that a current coil consists oia large conductor having only a few turns and very light insulation, so that much less space is taken by insulation, relative to the space occupied by copper, when a current coil is utilized. This makes it possible to utilize a smaller wattrneter element 55 than would be the case if it were provided with two voltage coils instead of one voltage coil and one current coil.

The voltage coil 60 of the voltage-restraint wattmeter element 55 is energized accordance with the phase-BC voltage of the voltage-supply conductors 31, in series with the break-contact 49 of the instantaneous phase overcurrent relay Ph. A and the three break-contacts 43 of the instantaneous unbalanced-current relay ClvlP, all connected in series, and it may be connected also in series with an external impedance device which may consist of a capacitor 66 and a resistor Bl which introduces a factor equal to the sine of the angle 4 between the phase-AC and phase-BC voltages, so that sin 1 becomes zero when the phase-AB voltage collapses.

The voltage-restraint torque produced by the wattmeter element 55 is thus the product of three factors, namely, the phase-AC voltage, the phase-BC voltage and the phase-AB voltage, so that the voltage-restraint is proportional to the area of the delta-voltage triangle of the line-voltages, and becomes zero whenever any one of these three delta-voltages becomes zero.

The power-directional torques produced by the three other wattmeter elements 56, 51 and 58 of the instantaneous phase directional relay CHV3 are all in a direction to actuate the relay so as to open the break-contacts 6! and close the makecontacts 52, when power is flowing into the line in the corresponding phase, A, B or C thereof, as will be readily understood from the connections illustrated. The wattmeter element 56, for instance, has its current coil 59 energized in accordance with the .hase-A line-current as sup plied by the current transformer 41, and it has its voltage element 60 energized in accordance with the phase-BC line-voltage as supplied by the voltage-supply line 3|.

In addition to the foregoing equipment, the following auxiliary elements are utilized.

Two auxiliary switches and 69 carried by the circuit breaker 7.--These are closed when the circuit breaker is closed and. open when the circuit breaker is open. The auxiliary switch 88 is in series with the trip coil so as to open the latter when the circuit breaker is open. The auxiliary switch 69 is connected between the negative bus and an auxiliary breaker-pcsition-responsive negative bus BN, to which some of the hereinafter-mentioned auxiliary-relaying equipment is connected.

An instmitancous auxiliary relay XI .--It is energized whenever there is an indication of current of fault-magnitude, and a direction of powerflow from the bus 3 into the line 2. It has one make-contact II and one break-contact 1-2.

An instantaneous auxiliary relay I T .-This is an instantaneous element associated with the backup timer Tl, about to be described. It has one make-contact 13.

A bac7c-up timer T1.-This is arranged to move slowly in the actuating direction, and to return to its initial position promptly, is indicated in the showng of a dashpot M connected to this timer relay Tl. It has two make-contacts Tl and TI of which the former may be so disposed that the contacts are made before the TI contacts are made, although this difference in time is not essential, as will be hereinafter pointed out in the explanation of the circuit-connections and operation of the device.

A carrier-failure time? TI.---This is provided with a dashpot l5 or any equivalent means for producing a slow pickup-rcsponse It is provided with one breakmontact IE and one make-contact i ll.

Au auxiliary relay Y7.'-This has one make-contact l8 and one break-contact Hi. It preferably has a slow pick-up of the order of three cycles of the line-frequency, r more, as indicated by the light dashpot 8B thereon, although this time delay is not vitally necessary, as will be explained in connection with the explanation of the operation hereinafter.

A11. out-of-step time lock-out relay T2.-It has a drop-out time long enough to allow the two ends of the line-section to pass through their out-ofphase condition while the line-losses being supplied by both ends, this drop-out time being possibly of the order of 10 or 15 cycles to a second, as will be subsequently described, and being obtained by means of a dashpot Si or any other timing means. This time lock-out relay T2 is provided with one break-contact 82,

Au oui--ogf--stcp auxiliary relay Z4.-This has one make-cont ct 83 and one break-contact 84.

An auxiliary carrier--maiutamiuy relay Y.-This has its operating coil 85 energized either in parallel or series with the trip coil it of the circuit breaker 4 for the parallel line the parallel connection being shown, that is, the relay coil 85 being connected in parallel to the trip coil 5. This relay has one maize-contact Bil. It is provided with any suitable means for giving it a short hesitation of about three cycles in its drop-out time, as indicated by the light dashpot 3?. The drawing also shows the corresponding relay Y for the parallel line i, the same having its operating coil 88 connected in parallel to the trip coil 8 of the circuit breaker l for the line 2.

A tripping push button 89 A contactor CS.-This is for the purpose of bypassing the llght relay-contacts which initially energize the trip-coil circuit 9, so as to prevent damage due to the heavy tripping current. This contactor has its operati J coil 9i connected in series with the trip coil 8 oi circuit breakor and it has one inake-contact which seals-in. the contactor keeps the trip circuit 9 energized until the cum it is finally interrupted by the auxiliary switch on the breaker.

The circuit connections of the above-described equipment are all shown Fig. l and are surnrnarized also in the schematic diagram of Fig. 2, which may be referred to for convenience in tracing out the operation of the apparatu Normally the instantaneous unbalanced-current relay Civil? and the instantaneous overcurrent relay Ph. A are in the deencrgized position, with their back contacts and 3 closed, thus maintaining voltage restraint on the phase directional relay GHVS at each end of the line-section 2. The voltage restraint is sufficient to overcome the action of the relay spring and to prevent the power-directional torques produced by normal loads from operating said relay CHVE, so that the relay contacts 6 I and 62 are normally in the positions shown.

Similarly, the pond directional relay CHB is no. aily deenergised by reason of the absence of residual power, as is also the ground overcurrent relay IQ, so that'the contacts of these relays are also in the positions shown, and this holds true for both ends of the line-section 2.

Reference to the top of Fig. 2 will show that these conditions normally maintain the plate circuit Chi-4332 of the transmitter H at each end of the line, and keeps the carrier current on the line.

Reference to the Ground protection trip circuit-in 2 ...1 show that the normally instantaneous trip circuit includes the ground-overcurllll]-l'8l9.y make-contact 33 and the ground-directional relay make-contact 38 in series, so that both of these contacts must be closedbefore either one can energize an auxiliary fault-responsive positive bus PP.

The remainder of the trip circuit includes the receiver-relay break-contact i 4 and the carrier- 1ailure-timer break-contact iii in series, from which the circuit is continued to the coil of the contactor CS and thence to the trip-circuit conductor t, the trip coil 8, and the auxiliary breaker- .switch 58 to the negative terminal.

As shown in Fig. 2 under the subject of Unbalanced protection, the auxiliary fault-responsive positive bus Fl? may also be energized by the closure of any one of the make-contacts 41 of the unbalanced-current relay CMP, the three inalie contacts 4'? being connected in parallel to each other and in series with the make-contact of the directional relay CHV3. It will be understood that it is necessary for the phase=-.

directional-relay malie-contact 62 to be closed before the auxiliary fault-responsive positive bus FF is energized by the actuation of any one of the three elements comprising the unbalanced-current relay CMP.

In 2, under the head of Three-phase protection, a circuit is also provided from the positive bus through the break-contact 84 of the auxiliary out-of-step relay Z4, in series with the Ph. A make-contact 5Q, thence to the CHV3 make-contact 82. The out-of-step relay contact 8 3 of the relay Z4 is shunted by the make-contact Ti" of the back-up timer Ti.

Under normal conditions, the receiver relay RR at each end of the line'section 2 is energized, so that its break-contact i is open, thereby interrupting the trip circuit, independently of the con dition of the relay contacts interposed between the positive bus the auxiliary fault-responsive positive bus PP.

When there is a fault involving ground, the instantaneous ground overcurrent relays Io in the line-sections adjacent to the fault will operate, closing the make-contacts 33 and 3 3. The makecontact by-passes the phase directional breakcontacts 6i thus giving preference to the ground relays in the control of the carrier current. This preference is desirable because load power may flow past a single line-to-ground fault, to a load beyond the fault, in sufficient amount to overbalance the torque due to the fault current, thus making it possible for one or more of the phase directic l elays CPU/'3 which are located at various on the system to give an incorrect -cation of the fault direction under this conion. Thus, if tr ground-fault preference is not inserted by the ground-current-responsive make-contact (i l, the improper opening of one of the phase directional relay contacts Si in any line-section would result in the interruption of the transmission of carrier current at a point where it should be maintained in order to provide correct relaying.

more of the Ph. A or in series with the voltage restraining winding 650 and remove the voltage restraint from the phase directional relay, allowing it to be operated by the load power, and if the fault is not in the line-section in question, the load power will be flowing into the line at one end and out of the line at the other, so that improper operation willbe obtained at one end.

In case a ground fault occurs on the protected line-section 2, the ground overcurrent relays It will be operated at both ends of the section. The ground directional relays CHB will also be operated at both ends, thus opening the plate circuits of the carrier-current transmitters and stopping transmission at both ends. This causes the receiver relays HR at both ends to be deenergized, thus closing their break-contacts i 4 and completing the trip-circuits through the contacts 33 and 38 of the ground overcurrent reiay I0 and the ground directional relay CHE at each end of the line.

If the fault involves more than one conductor and the ground fault-current is insufficient to operate the ground overcurrent relay Io, the control of the carrierecurrent transmission resides in the phase directional relay CHVS. If the fault is in the protected line-section 2, the phase directional relay CHV3 at each end of the section will interrupt the transmission of carrier current, this relay being now free to operate be cause of the removal of voltage restraint by reason of the low voltage due to the fault itself or by reason of the removal of all voltage restraint by the actuation of the P11. A relay or one of the CMP relay elements. As soon as carrier is removed from both ends of the line-section, the receiver relay RR at each end Will be deenergized, closing its break-contact l4 and completing the trip circuit, in this case, through the contact 62 of the phase directional relay and the contacts 41 or 58 of the unbalanced current relay CMP or the Ph. A relay, according as the fault is an unbalanced fault or a three-phase fault.

Under some extreme conditions of system operation, it may happen that the fault currents flowing to the fault from one end of the line will be insufficient to operate the overcurrent relays at that end, until after the circuit breaker at the opposite end has opened. In order to permit instantaneous tripping at said opposite end, however, it is necessary that the transmission of carrier current be interrupted at both ends. This is accomplished at the end carrying the small tional relay will, therefore, be operated by residual-voltage bias, because the ground current is small, and the back contact 31 will be opened under this condition, thereby interrupting the carrier-current transmission. At the opposite end of the line there will necessarily be ground current as well as residual voltage, so that the apparatus will perform in the usual manner, as previously described, and the tripping will occur at that end as soon as the receiver-relay contact 14 closes. As soon as the circuit breaker opens, clearing the fault at the end carrying the rat current, the current at the end which orig 1y carried the small amount of fault current will usually rise above the tripping value and tripping will follow immediately.

If the fault involves more than one conductor, one or more of the phases of the delta at the end carrying the small current duced to a low value, thereby removing the voltage-restraint from the phase directional relay CHV3, and this relay will be operated by its spring 63, aided by the slight power-directional torque produced by the small value of fan? .rent. The operation of this relay opens the contact BI and since the ground current is small, the ground over-current relay contact will e on main open, so that the transmitter plat will be interrupted, thus interrupting the oper tion of the carrier-current 'ransmitter at that station. In other respects, the clearing of such faults is similar to the clearing of the ground faults just discussed.

In the case of an external ground fault produc ing ground current flowing in the direction from the bus 3 into the line 2, but where the fault is located externally of the line-section 2, the ground directional relay CHB at the bus 3 will be actuated, opening its contact 31 and interrupting the transmitter plate circuit, thus intcrrupting the operation of the carrier-current trans mitter l l at that station. At the other end of the line-section 2, however, the ground power-flow will be from the line to the bus, so that the ground directional relay CHB at that station will not be actuated, the torque being in the direction to keep its normally closed contacts El closed more tightly, so that the carrier-current transmission at this station will be maintained. Therefore, the receiver relays RR will remain energized at both stations and will keep the trip circuits open at the relay contact M at both stations.

In the case of a multi-conductor fault at the same location, which does not involve ground or in which the ground current is so small that the ground overcurrent relay I0 is not actuated, the operation will be as follows. At the station shown in the drawings, fault power flowing from the bus 3 into the line 2 will cause the operation of the phase directional relay CHVB in the normal manner, and since the ground overcurrent relay I0 is not actuated, the opening of the phase directional relay contact Bl will interrupt the transmitter plate circuit and thus interrupt the carrier-current transmitter at this station, but the carrier-current transmission will be maintained at the station at the other end of the linesection 2, so as to prevent tripping.

In case oi external faults outside of the line section 2, but in such direction that the fault power is flowing from the line into the bus 3, the operation will be the same as described above, except that the stations at the two ends of the line-section 2 will be interchanged in the description.

Out-of-synchronism conditions have, in times past, presented a difiiculty, in any kind of pilot relaying, whether utilizing continuous carrier, intermittent carrier, or pilot wires, because, at one or more points in the transmission system, which are called electrical centers, it may appear that power is flowing into these points just as if there were a three-phase "fault at each of these points, so that any relaying system responsive to threephase faults would respond to such out-of-synchronism conditions so as to trip out the line-sections containing these electrical centers of the distribution system. In the relaying system shown in the drawings, means have been provided for ailording out-oi-step protection, and preventing iaulty relaying operations under these conditions. Said means, and the method of operation involved thereby, constitutes the subjectmatter of an application of William A. Lewis, Serial No. 703,606, filed December 22, 1933, for Out-of-step protection. In order to make the description of the entire relaying system complete in this application, the following description oi the out-of-step protection is included.

During the early stages of out-of-step operation, the two ends of each line-section begin gradually to swing apart in phase, increasing the phase-angle between the two ends until exact phase opposition is reached at and then on through to 360, and then repeating the cycle, requiring a time which may be of the order of a second or several seconds to complete a cycle, dependent upon the system-constants and the operating conditions of the system.

Out-oi-synchronism conditions are recognized by the fact that, during the early stages, power flows through each. line-section from one end to the other in a manner similar to an external fault, the current increasing from loadmagnitude to fault-magnitude as loss of synchronism is approached. As the power-sources feeding the two ends of the line-section reach approximate phase-opposition, there will be no change in power-flow in those sections which do not contain an electrical center.

But where an electrical center of the system falls in any particular line-section, there will be a brief period in the out-oi-synchronism cycle of the transmission system, lasting from just before until just after the 180 phase position is reached, when the losses of the line are being supplied at both ends of the line-section, so that power of fault-magnitude flows into such a line-section from both ends, thus momentarily simulating an internal three phase fault. This is a condition of unstable equilibrium and will not be maintained, returning again to a through-condition, with power ilowing in at one end and out at the other end of the line-section, soon after the condition of exact phase-opposition is past, so that if. the tripping sequence of the three-phase faultresponsive devices is momentarily opened by a time-delay relay energized before the condition of phase-opposition is reached, tripping will be prevented.

In the illustrated relaying system, as the two sources pull out of synchronism, power flows through the relayed section 2 at the same time that current of fault-magnitude is approached. Under this condition, the voltage restraint is removed irom the phase directional relay CHVS", and carrier is removed from the end where power flows into the section. At the other end of the section, however, power is flowing out, and consequently carrier is maintained at that end. This condition is recognized by the continuance of a three-phase over-current for a time long enough wherever it Referring to 2, under the heading of Outof-step protection, it will be noted that a relay Y1 is provided, having a slightly delayed pick-up action, so that it will be actuated if the receiver relay RR remains energized, so that the RR contact 1B stays closed, for a predetermined time after an overcurrent condition exists, as indicated by the picking up of the overcurrent relay Ph. 0 which closes its contact 52. The time-hesitation in the pick-up of the relay Y'i need be only of the order of two or three cycles of the fundamental line frequency, or slightly more, so that if the over-current condition arose as a result of an internal fault in the protected line-section, tripping could occur, as will be subsequently pointed out. It will be observed that the tripping circuit of the relay Y1 extends from the positive bus, through the receiver-relay contact it, to the con ductor RC, thence to the 'Ph. C" relay-contact 52 and the operating coil of the relay Yi, to the auxiliary breakerposition-responsive negative bus EN which is connected to the negative bus by the breaker auxiliary switch as long as the breaker remains closed.

As soon as the out-of-step relay Y7 picks up, it closes its contact 18 and thus completes a circuit from the positive bus to the tripping coils of both the out-ofstep time loclnout relay T2 and the auxiliary out-of-step relay Z 3. The energization of the relay Z t immediately closes a holding circuit through the Z? relay-contact 83, by-passing the Y1 relay-contact 58. The relay Z 2 also interrupts the three-phase fault-responsive tripping circuit by reason of the opening of the Z relay contact 84. The Z4 relay pick-up time, from the first energization of the Y1 coil, that is, from the firstactuation of the overcurrent relays Ph. A and Ph. C, must be longer than it would take to close the trip contact 92 of the contactor CS in case of a three-phase fault, which may be of the order of two cycles.

The out-of-step timing relay T2 is of the instantaneous pick-up type, with time-delay reset. Its actuating coil is by-passed by the Y1 relaycontact 19 which closes when the Y1 relay is deenergized. The T2 relay has a back-contact 82 which closes after a predetermined time-delay upon the deenergization of the relay T2, and the circuits are such that when the back-contacts iii and 82 of both Y1 and T2 are closed the actuating coil of the Z4 relay will be sh0rt-circuited, thus deenergizing the latter, reclosing the Z4 back-contact lit, in the tripping circuit, and opening the Z4 holding circuit at If there is not an electrical center in the linesection 2 being protected, the receiver-relay front-contact id will remain closed throughout the out-of-synchronism condition, and the overcurrent relay Ph. 0 contact 52 will remain closed until near the end of the out-of-synchronism cycle, when the two sources at the two ends of the line will again approach iii-phase position. As the two sources vary in speed, they will change successively from in-phase position to out-o1- phase position, resulting'respectively in the alterinate deenergization and energization of the Y1 irelay, following the slip frequency. There is no needfor outof-step protection under these cirentai cumstances, because we have assumed a line-seiz tion in which there is no electrical center hence in which there is never a condition of the simultaneous flowing of power of fault-magnitude into both ends of the line-section.

If an electrical center of the transmission system should fall within the line-section 2 being protected, there will be a brief time, near the condition of exact phase-opposition of the two sources, when power of fault-magnitude will flow into both ends of the line-section, thus operating both of the phase directional relays CHV3 and interrupting carrier-current transmission at both ends, so that each of the receiver relays RR is deenergized. The deenergization of the receiver relay RR opens its contact 16 and deenerglass the Yl relay, thus short-circuiting the energizing coil of the T2 relay by the closure of the Y? relay back contact 19.

The T2 relay then starts drop-out time (plus the Y1 must be of the order of 10 or 15 cycles to a second, or long enough to permit riding over that portion of the out-of-step cycle in which the relaying conditions are three-phase fault, or until relays CHVSl at the two ends of the line-section again register an external fault, that is, with one of the relays registering power flowing into the line and the other registering power flowing out of the line, thus restoring carrier-current transmission. to one end of the line, picking up the receiver relays RR at both ends of the line. At this time, the Y1 relay is again energized, thus removing its short-circuit 19 from the operating coil of the T2 timing relay and permitting the latter relay to move its back-contact 82 wide open before it has had time to become closed. The T2 timing relay will thus be kept in its energized position, and its back-contact will not close during the out-of-synchronism condition. As long as the TZ-relay back-contact 82 does not close, the Z4 relay will remain energized and will, in turn, prevent tripping by reason of its open back-contact 84 in the tripping circuit of the three-phase fault-responsive device.

It has been recognized that an out-of-step condition may simulate a three-phase fault not involving grounds and that, therefore, the unbalanced-current fault-responsive relay, as well as the ground protection, will not be, involved. teference to Figs. 1 and 2 of the drawings will show that the Z4 relay contact 84 is in series with only that portion of the tripping circuit which is responsive to three-phase faults. It does not interfere with the response to unbalanced phase faults or ground faults. Thus, if either a ground fault or an unbalanced phase fault should occur to drop out, and its relay drop-out time) in the drop-out time of the T2 timing relay.

It will now be appreciated why the Y1 relay slow pick-upof at least to close the trip contacts 92 of the contactor CS in case of a three-phase fault, which is of the order of two cycles. This is so, because as soon as the Z4 relay picks up, its back-contact 84 opens and prevents tripping as a result of a three-phase fault.

The relaying system shown in the drawings also provides for back-up protection. Referring to Fig. 2, under the heading of Back-up protection it will be noted that the XI relay coil is energized whenever the energization of the auxiliary fault-responsive positive bus FP indicates the presence of a fault with fault-power flowing from the bus 3 into the line 2. The energization of the operating coil of the XI relay is completed from the FP bus, through this XI coil, to the auxiliary negative bus BN.

Whenever there is current of fault-magnitude, accompanied by fault power-direction from the bus to the line, whether the fault is an internal fault within the line-section 2, or an external fault outside of it, the XI relay will be energized, and its front-contact II will energize the operating coils of both the back-up timer TI and its instantaneous auxiliary relay IT. The front contact 13 of the instantaneous relay IT will complete a holding circuit for the relay IT and the timer TI, provided that it is a three-phase fault which actuated the XI relay, as indicated by the energization of the Ph. C relay, resulting in the closure of the Ph. C relay-contact I. This holding circuit 5I-'I3 is necessary in order to main tain the energization of the TI timer even after the interruption of the energization of the faultresponsive relay XI, because such an interruption of XI may be brought about by the actuation of the relay Z4 of the out-of-step protective system. By this means, the timer TI will remain energized after the energization of the out-of-step protective elements.

Thus, if there were a three-phase fault in the second line-section, that is, in the line-section to the right of the right-hand end of the line-section 2 shown in the drawings, the operations of the back-up protective features on the line 2 would not be cut-off by the Z4 out-of-synchronism relay.

The back-up-timer TI is set to have a time of operation long enough to permit normal tripping in the second section, for example, if the fault is in the second section, whether the fault is a ground fault, an unbalanced fault, or a threephase fault. This time will include both the relay time and the necessary circuit-breaker time, it being understood that quick-acting circuit breakers, as quick as three cycles or even less, will be utilized. If the fault is not cleared in a predetermined time which is longer than that necessary for it to be cleared if the relaying equipment is operating properly, the back-up timer TI will close its first contact TI which by-passes the circuit containing the receiver-relay back-contact I4 and the carrier-failure-timer back-contact I6, so that tripping will be effected even though carrier current is not removed from the line, that is, even though the receiver relay RR remains energized, with its back-contact I4 open.

At the close of the pick-up movement of the back-up timer TI, it closes its second contact TI", which by-passes the Z4 contact 84 of the out-of-step protection, and makes it possible to clear a three-phase fault through the back-up tripping contacts TI and TI. The time-delay in the closure of the TI" contact may be very great, of the order of several seconds or even minutes, in order to insure that the circuit breaker 1 is not tripped during the continuance of any possible or probable out-of-synchronism condition. No such great time-delay is necessary, however, in the back-up protection for faults involving grounds or unbalanced currents, and hence the TI back-up timer contacts may close in a much shorter time, merely long enough to permit the fault to be cleared by some other circuit breaker, if it is going to be cleared at all, before the operation of the back-up timer contact TI makes it possible to clear the fault by means of the circuit breaker l which is being controlled.

An important advantage of the continuous carrier system over the intermittent carrier system is that the continuous carrier system may readily embody means for quickly indicating any fault in the carrier-current apparatus, whether transmitter or receiver, as soon as it occurs, whereas, in an intermittent carrier system, such a fault may not become evident until an occasion arises for putting the carrier onto the line in order to prevent tripping, in which case its failure will result in a faulty tripping operation, which is the first notice which the station-operator has of the carrier-current failure. The carrier-failure indication shown in the drawings is similar to that which is shown and covered in the previously mentioned Lewis and Evans application Serial No. 660,342.

Referring to Fig. ings, under the heading of Carrier failure indication, it will be noted that a circuit is completed from the positive bus to a conductor marked T33 upon the deenergization of either the receiver relay RR or the transmitter supervisory relay TS, closing their back contacts I5 and I2 respectively. If, at the same time that the T83 conductor is energized, there is not a fault on the line-side of the bus 3, the XI relay will not be energized, and the back-contact 12 of the latter will be closed, completing a circuit from the T83 conductor to the operating coil of the carrier-failure timer T3, from which the circuit is completed to the auxiliary negative bus BN. After a suitable time-delay, which is longer than the longest tripping time of the back-up protection, the carrier-failure timer TS will complete its pick-up movement and will close its frontcontact 11, completing a circuit from the TS3 conductors to an alarm, at the same time opening its back-contact I6 in the tripping circuit, thus permanently looking out, the receiver-relay tripping contact I4 and thereafter permitting tripping only as a result of the back-up protection afforded by the TI contact, until the stationattendant, aroused by the alarm, has had time to discover and correct the cause of the carrierfailure.

In accordance with my invention, the illustrated protective relay system includes another feature which is designed to afford protection in the event of a sudden reversal of fault-current in a sound line when the line breakers at the two ends of a faulty line do not open simultaneously. This condition will be made clear by reference to the single-line diagrams of Figs. 3 and 4, wherein a transmisison system is shown involving a source S, feeding a bus 3 which, in turn, feeds line-sections I and 2 through circuit reakers 4 and "I respectively. The opposite ends of the line-sections I and 2 are connected to a bus IOI through circuit breakers I02 and I03 respectively, and the bus IN is, in turn, connected to additional line-sections I04 and I05 through breakers I06 and I01. The far ends of the line- 2 of the accompanying drawsections I 04 and I05 are a second source S.

Referring to'Fig. 3, if a fault the far end of the parallel line-section l, the fault-power will flow in the direction shown by the arrows. It will be noted that the power-flow is from the buses 3 and I 9 5, respectively, into the faulty line I, at both ends, so that carrier is removed from both ends, and instantaneous tripping is permitted. In the sound line 2, however, the fault-power is flowing from the bus- 3 into the line, thus removing carrier from that end of the line, but the fault-power is flowing from the line to the bus ml at the other end, thus maintaining carrier at that end and'preventing the tripping oi the breakers l and 83 at the two ends of the sound line 2.

In the faulty line I, the two circuit breakers stantially simultaneously breakers begin arcing at substantially the same time, but it is almost inevitable that the breaker carrying the heaviercurrent, which would generally be the breaker Hi2 closest to the fault, would cease arcing a hali cycle or more ahead of the other breaker, or that one breaker would cease arcing in one of its poles before its other poles, so that there would or might be a sudden reversal of fault-current in the sound line.

Thus, if the breaker i552? opens before the breaker 4 in the faulty line, the conditions will be as depicted in Fig. i. It will be noted, from the arrows, that the current has reversed at both ends of the sound line This means that the far end containing the breaker I03, which was at first maintaining the carrier, so as to prevent tripping, will, if nothing is done to prevent it, stop transmitting carrier as soon as either one of its directional relays CHE or CI-IV3 backs on" of its back-contact 3'? or 6|, as the case may be. However, at the near end of the sound line 2, where the circuit breaker 'l is located, the directional element CHE or CI-IiV3 which has responded to the fault-power-fiow shown in Fig. 3, has moved to the extreme limit or" its travel, with its back-contact 37 or 6 I, as the case may be, wide open, and it has to move much further than the corresponding relay at the far end where the circuit breaker its is, before the previously open back-contact can be reclosed, thus restoring carrier. It is almost inevitable, therefore, that there will be a half-cycle or several half-cycles during which carrier will be removed from the sound line 2, thus permitting the tripping of it connected eventually to bl'llS sound possible, because such faulty tripping would be very likely to cause a serious interruption in service.

Means for overcoming this difficulty constitutes the subject-matter of the present application, which is directed particularly to the problems of continuous carrier-current relaying. some of the general principles of preventing faulty operation as the result of non simultaneous operation of breakers or of the different poles of a polyphase breaker are also covered in an application of Edward H. Klemmer, Serial No. '703,6G9,'filed December 22, 1933, for Relaying systems.

Referring to Figs. 1 and 2 of the accompanying drawings, it will be seen that the carrier-current transmission is protected by an auxiliary'relay Y, the operating coil of which is'energized whenever the tripping circuit of the breaker 4 in the parallel line i is energized, or, in other words, upon theenergization of any tripping circuit of any circuit breaker attached to the bus 3, other than the circuit breaker l which is being controlled. The auxiliary relay'Y is'provided with a make-contact 86 which by-passes all of the relay contacts which transmitter plate circuit of the transmitter H, thereby insuring the maintenance of carrier-current transmission on the line 2. This Y relay may be provided with means, symbolized bythe light dashpot 87, for causing it to delay two or four cycles in its drop-out, so as to introduce that much time-hesitation in the carrier-current tripping functions of the sound line 2 after the opening of the circuit breaker 4 in the faulty line I under the conditions previously outlined. In the normal operation of the protective equipment for the line 2, the auxiliary relay Y will not be involved, because its operating coil 85 will not be energized in response to a fault involving power-flow from the bus 3 into the line 2.

As is customary in carrier current relaying systems, a suitable carrier-frequency trap is utilized in the phase-conductor or conductors to which the carrier is coupled. In the particular form of embodiment shown in the drawings, this trap consists of an inductance coil 2% shunted by a capacitor 2d! and a lightning arrester 2M.

While I have shown my invention in a single illustrative form of embodiment, it will be understood that various mcdifications and alterations may be resorted to, as will be more or less obvious to those skilled in the art, without departing from the general basic principles of my inven tion. I desire, therefore, that the appended claims shall be accorded the broadest interpretation con-- sistent with their language and the prior art.

I claim as my invention:

1. An electrical transmission system including a plurality of linesections, a relaying station, a bus at the relaying station having a plurality of said line-sections connected thereto, each of said bus-connected line-sections having circuit-interrupter means interposed between itself, and the bus, and tripping means for actuating each of said circuit-interrupter means, characterized by protective means for one of said line-sections, said protected line-section having line-sectionalizing circuit-interrupter means at each end thereof, and said protective means comprising relaying means at each section and including a communicating channel between the two ends or the line-section, said relaying means including quick-acting relaying means associated with the circuit-interrupter means at both ends of the protected line-section and also associated with the communicating channel therebetween for tripping said circuitinterrupter means in the event of a fault accompanied by power-direction into the protected line-section at both ends thereof, and means responsive to the energization of the tripping means on another of the circuit-interrupter means associated with said bus for interposing an impediment against the subsequent immediate quick tripping of a circuit-dnterrupter means of the protected line-section.

2. Protective relaying equipment for eirecting a control of line-sectionalizing circuit-interrupter means for a transmission linesection, comprising, at each end of the line-section being protected, relaying means including a direction ally responsive quick-actihg relaying means for responding selectively to faults accompanied by fault-power-flow into the protected line-section, a communicating channel between the two ends might open-circuit the end of the protected lineof the line-section being protected, a transmitter means disposed at each end of the linesection for normally continuously transmitting a signalling current through said communicating channel to the other end of the line-section, transmitter-controlling means responsive to said directionally responsive quick-acting relaying means for causing said transmitter to cease transmitting effective signalling currents, a receiver disposed at each end of the line-section and associated with said communication channel, means at each end, responsive to a failure of the receiver to receive a sufficient signalling current, and responsive also to the direction of powercurrent flow into the line-section being protected, for quickly energizing a control circuit for the circuit-interrupter means, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuitinterrupter means, and means responsive to the energization of this last-mentioned tripping means for interposing an impediment against the subsequent immediate quick tripping of a circuitinterrupter means of the protected line-section.

3. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, relaying means including a directionally responsive quick-acting relaying means for responding selectively to faults accompanied by fault-power-fiow into the protected line-section, a communicating channel between the two ends of the line-section being protected, transmitter means disposed at each end of the line-section for normally continuously transmitting a signalling current through said communicating channel to the other end of the line-section, transmitter-controlling means responsive to said directionally responsive quick-acting relaying means for causing said transmitter to cease transmitting effective signalling currents, a receiver disposed at each end of the line-section and associated with said communication channel, means at each end, responsive to a failure of the receiver to receive a sufficient signalling current, and further responsive to the actual presence of a fault on the transmission line, and responsive also to the direction of power-current flow into the line-section being protected, for quickly energizing a control circuit for the circuit-interrupter means, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for interposing an impediment against the subsequent immediate quick tripping of the circuit-interrupter means of the protected line-section.

4. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupternieans for a transmission line-section, comprising, at each end of the line-section being protected, relaying means including a directionally responsive quick-acting relaying means for responding selectively to faults, a communicating channel between the two ends of the line-section being protected, means responsive to said directionally responsive quick-acting relaying means for transmitting a signal through said communicating channel to the other end of the line-section, means, at each end, responsive to said signal, and responsive also to the direction of power-current flow into the line-section being protected, for quickly energizing a control circuit for the circuit-interrupter means of the protected line-section, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for interposing an impediment against the subsequent immediate quick tripping of a circuit-interrupter means of the protected line section.

5. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising at each end of the line-section being protected, relaying means including a directionally responsive quick-acting relaying means for responding selectively to faults, a communicating channel between the two ends of the line-section being protected, means responsive to said directionally responsive quick-acting relaying, means for transmitting a signal through said communicating channel to the other end of the line-section, means, at each end, responsive to said signal, and further responsive to the actual presence of a fault on the transmission line, and responsive also to the direction of power-current flow into the line-section being protected, for quickly energizing a control circuit for the circuit-interrupter means of the protected linesection, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for interposing an impediment against the subsequent immediate quick tripping of a circuit-interrupter means of the protected line-section.

6. Protective equipment for a transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults, time-delay tripping-means associated with each of said fault-responsive relaying means for actuating its associated circuitinterrupter means after a time-delay, means for providing an intelligence-communicating channel between the two ends of the line-section being protected, auxiliary means associated with said intelligence-communicating channel for se lectively responding to conditions of faults somewhere between the two ends of the particular line-section being protected for so modifying the action of said time-delay relaying means as to substantially eliminate its time-delay, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for interposing an impediment against the subsequent immediate quick tripping of a circuit-interrupter means of the protected line-sec- '1. Protective equipment for a transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protecteach of said relaying means including quick relaying means directionally responsive to certain faults accompanied byfault-po-wer-flow into the protected line-section, and time-delay trippingmeans associated with each of said fault-responsive relaying means for actuating its associated circuit-interrupter means after a time-delay, in combination with transmitter means at each end of the line-section being protected for normally transmitting a signalling current, receiver means at each end of the line-section for receiving the signalling current transmitted from the other end, each of said receiver means having contact means for quickly short-circuiting the time-delay means at its end in response to a cessation of a suiiicient received current, means quickly operative at each end of the line-section being protected, in response to the directionally responsive relaying means at that end, for so affecting said transmitter signalling means at that end as to cause the receiving means at the other end to fail to receive its sufficient received current from the transmitter at the first end, a bus connected to one end of the protected line-section and having and another circuit-interrupter means therefor connected to said'bus, controlling means for tripping said other circuitinterrupter means, and means responsive to the energization of this last-mentioned tripping means for interposing an impediment against the subsequent immediate quick tripping of a circuitinterrupter means of the protected line-section.

8. Protective equipment for a transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults accompanied by fault-power-flow into the protected line-section, and time-delay tripping-means associated with each of said fault-responsive relaying means for actuating its associated circuit-interrupter means after a timedelay, in combination with transmitter means at each end of the line-section being protected for normally transmitting a signalling current, receiver means at each of the line-sections for receiving the signalling current transmitted from its own end as well as the other end, each of said receiver means having contact means for quickly short-circuiting the time-delay means at its end in response to a cessation of a suficient received quickly operative at each end of the line-sectin being protected, in response to the directionally responsive relaying means at that end, for so affecting said transmitter signalling means at that end as to cause the receiving means at each end to fail to receive its sufiicient responsive to the energization of this last-mentioned tripping means for interposing an impediment against the subsequent immediate quick tripping of a circuit-interrupter means of the protected line-section.

9. Protective relaying equipment for eifecting a control tected, relaying means including ad'irec'tionally responsive quick-acting relaying means for responding selectively to faults accompanied by fault-power-fiow into the protected line-section, a communicating channel between the two ends of the line-section being protected, a transmitter means disposed at each end of the line-section for normally continuously transmitting a signalling current through said communicating channel to the other end of theline-section, transmitter-controlling means responsive to said directionally responsive quick-acting relaying means for causing said transmitter to cease transmitting effective signalling currents, a receiver disposed at each end of the line line-section and associated with said communication channel, means at each end, responsive to a failure of the receiver to receive a sufficient signalling current, and responslve also to the direction of power-current flow into the line-section being protected, for quickly energizing a control circuit for the circuit-interrupter means, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter therefor means connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for causing said transmitter to transmit said suflicient signalling current.

10. Protective relaying equipment for effecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the lines-section being protected, relaying means including a directionally responsive quick-acting relaying means for responding selectively to faults accompanied by fault-powerflow into the protected line-section, a communieating channel between the two ends of the linesection being protected, transmitter means disposed at each end of the line-section for normally continuously transmitting a signalling current through said communicating channel to the other end of the line-section, transmitter-controlling means responsive to said directionally responsive quick-acting relaying means for causing said I transmitting effective signalling currents, a receiver disposed at each end of the line-section and associated with said'communication channel, means at each end, responsive to a failure of the receiver to receive a sufiicient signalling current, and further responsive to the actual presence of a fault on the transmission line, and responsive also to the direction into theline-section being protected, energizing a control circuit for the circuit-interrupter means, a lous connected to one end of the protected line-section and having another power line and another circuitinterrupter means thereforconnected to said bus,

controlling means for tripping said other circuitinterrupter means, and means responsive to the energization of this last-mentioned tripping means for causing said transmitter to transmit said suiiicient signalling current.

11. Protective relaying equipment for eifecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at'each end of the line-section being protected, directionally respon tested, means responsive mitting a signal through said communicating channel to the other end of the line-section, means, at each end, responsive to said signal, and responsive also to the direction of powercurrent flow into the line-section being protected, for quickly energizing a control circuit for the circuit-interrupter means of the protected linesection, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for maintaining said communicating channel in such condition as to interpose an impediment to a quick energization of the circuit-interrupter means at either end of the protected line-section.

12. Protective relaying equipment for eifecting a control of line-sectionalizing circuit-interrupter means for a transmission line-section, comprising, at each end of the line-section being protected, relaying means including a directionally responsive quick-acting relaying means for responding selectively to faults, a communicating channel between the two ends of the line-section being proto said directionally responsive quick-acting relaying means for transmitting a signal through said communicating channel to the other end of the line-section, means, at each end, responsive to said signal and further responsive to the actual presence of a fault on the transmission line, and responsive also to the direction of power-current flow into the line-section being protected, for quickly energizing a control circuit for the circuit-interrupter means of the protected line-section, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for maintaining said communicating channel in such condition as to interpose an impediment to a quick energization of the circuit-interrupter means at either end of the protected linesection.

13. Protective equipment for a transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults, time-delay tripping-means associated with each of said fault-responsive relaying means for actuating its associated circuit-interrupter means after a time-delay, means for providing an intelligence-communicating channel between the two ends of the line-section being protected, auxiliary means associated with said intelligencecommunicating channel for selectively responding to conditions of faults somewhere between the two ends of the particular line-section being protected for so modifying the action of said timedelay relaying means as to substantially eliminate its time-delay element, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for maintaining said communicating channel in such condition as to interpose an impediment to a quick energization of the circuit-interrupter means at either end of the protected line-section.

14. Protective equipment for a transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults accompanied by fault-power-flow into the protected line-section, and time-delay tripping-means associated with each of said faultresponsive relaying means for actuating its associated circuit-interrupter means after a timedelay, in combination with transmitter means at each end of the line-section being protected for normally transmitting a signalling current, receiver means at each end of the line-section for receiving the signalling current transmitted from the other end, each of said receiver means having contact means for quickly short-circuiting the time-delay means at its end in response to a cessation of a sufficient received current, means quickly operative at each end of the line-section being protected, in response to the directionally responsive relaying means at that end, for so affecting said transmitter signalling means at that end as to cause the receiving means at the other end to fail to receive its sufiicient received current from the transmitter at the first end, a bus connected to one end of the protected linesection and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for causing said transmitter to transmit said sufficient signalling current.

15. Protective equipment for a transmission line section, comprising line sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults accompanied by fault-power-fiow into the protected line-section, and time-delay trippingmeansassociated with each of said fault-responsive relaying means for actuating its associated circuit interrupter means after a time-delay, in combination with transmitter means at each end of the line-section being protected for normally transmitting a signalling current, receiver means at each end of the line-section for receiving the signalling current transmitted from its own end as well as the other end, each of said receiver means having contact means for quickly shortcircuiting the time-delay means at its end in response to a cessation of a suflicient received current, means quickly operative at each end of the line-section being protected, in response to the directionally responsive relaying means at that end, for so affecting said transmitter signalling means at that end to cause the receiving means at each end to fail to receive its sufiicient received current from the transmitter in question, a bus connected to one end of the protected linesection and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for causing said transmitter to transmit said sufficient signalling current.

16. Protective equipment for a transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults, means for providing an intelligence-communicating channel between the two ends of the line-section being protected, auxiliary means associated with said intelligence-communicating channel for selectively cooperating with the directionally responsive means at the two ends of the protected linesection so as to respond to conditions of internal faults somewhere between the two ends of the particular line-section being protected for actuating the circuit-interrupter means at both ends of the protected line-section, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentionedtripping means for interposing an impediment against the subsequent immediate quick tripping of a circuit-interrupter means of the protected line-section;

17. Protective equipment for a transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults accompanied by fault-poWer-fiow into the protected line-section, in combination with transmitter means at each end of the linesection being protected for normally transmitting a signalling current, receiver means at each end of the line-section for receiving the signalling current transmitted from its own end as well as the other end, each of said receiver means having contact means for quickly actuating its associated circuit-interrupter means in response to a cessation of a suiiicient received current, means quickly operative at each end of the linesection being protected, in response to the directionally responsive relaying means at that end, for so affecting said transmitter signalling means at that end as to cause the receiving means at each end to fail to receive its sufiicient received current from the transmitter in question, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for interposing an impediment against the subsequent immediate quick tripping of a circuit-interrupter means of the protected line-section.

18. Protective equipment for a transmission "line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults, means for providing an intelligence-communicating channel between the two ends of the line-section being protected, auxiliary means associated with said intelligencecommunicating channel for selectively cooperating with the directionally responsive means at the two ends of the protected line-section so as to respond to conditions of internal faults somewhere between the two ends of the particular line-section being protected for actuating the circuit-interrupter means at both ends of the protected line-sectiona bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuitinterrupter means, and means responsive to the energization of this last-mentioned tripping means for maintaining channel in such condition as to temporarily interpose an impediment to a quick energization of the circuit-interrupter means at either end of the protected line-section.

19. Protective equipment for a transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults, means for providing an intelligence-communicating channel between the two ends of the line-section being protected, auxiliary means associated with said intelligence-communicating channel for selectively cooperating with the directionally response means at the two ends of the protected line-section so as to respond to conditions of internal faults somewhere between the two ends of the particular line-section being protected for actuating the circuitinterrupter means at both ends of the protected line-section, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means there-- for connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this lastmentioned tripping means for interposing an impediment to a quick energization of a circuit-interrupter means of the protected line-section.

20. Protective equipment fora transmission line-section, comprising line-sectionalizing circuit-interrupter means and relaying means therefor at each end of the line-section being protected, each of said relaying means including quick relaying means directionally responsive to certain faults accompanied by fault-power-flow into the protected line-section, in combination with transmitter means at each end of the linesection being protected for normally transmitting a signalling current, receiver means at each end of the line-section for receiving the signalling current transmitted from its own end as well as the other end, each of said receiver means having contact means for quickly actuating its associated circuit-interrupter means in response to a cessation of a suflicient'received' current, means quickly operative at each end of the line-section being protected, in response to the directionally responsive relaying means at that end, for so affecting said transmitter signalling means at that end as to cause the receiving means at each end tofail to receive its sufiicient received current from the transmitter in question, a bus connected to one end of the protected line-section and having another power line and another circuit-interrupter means therefor connected to said bus, controlling means for tripping said other circuit-interrupter means, and means responsive to the energization of this last-mentioned tripping means for causing said transmitter to transmit said sufficient signalling current. 

